The present invention relates to a metal cored board and a method for producing the same, which is used suitably for preparing a hybrid integrated circuit.
The recent outstanding trend in the electric and electronic field is to make smaller the size of various devices and apparatus with using a compact hybrid integrated circuit. Under the trend it becomes very important problem to be solved to release efficiently the Joule's heat generated from the circuit. Especially, heat-releasing in the portion mounting a silicon chip and like semiconductive element is more important and urgent, because in general such a semiconductive element is very sensitive to heat and deteriorates or miss-operates possibly at a high temperature surroundings.
The hybrid integrated circuit is mounted usually on a wall or base of an apparatus, and in this mounting hitherto, the metal core of the circuit has been screwed down to the apparatus. The circuit fixed by the method is demountable to be advantageous for repair and inspection. However, this mounting method has a fatal shortcomming, that is, even if tightly screwed, there remains always an air layer of micron order between the metal core and the apparatus. The air layer prevents the Joule's heat from efficient release. In addition, the screw frequently loosens gradually in the course of operating the apparatus, or is loosened by vibration of the apparatus to increase the air gap.
The present inventors discovered that the metal core is soldered to the apparatus in order to improve thermal conductivity therebetween. The idea, however, is difficult to put it in practice for the following reason. Namely, the metal core is composed in general of aluminium, iron, and like base metals from economical standpoint, and those base metal are difficult to be soldered or requires special techniques for soldering, because of easy oxidizable characteristics thereof.